A. Field of Invention
This invention relates to noise cancellation systems, and is directed particularly, but not solely, towards a headphone noise cancellation system.
B. Description of the Related Art
It is known to provide noise compensation systems with either noise cancellation built into the headphone or with a fixed noise cancellation system forming part of the system into which a headphone is plugged. U.S. Pat. No. 5,182,774 exemplifies the former type which have the noise cancellation tailored to each headphone type. The latter have previously been designed for use with only one manufacture of headphone and the noise cancellation is problematic with other types because of variations in frequency response and impedance which render the cancellation ineffective and can, at worst, result in positive feedback and instability.